U.S. Pat. No. 4,253,613issued on Mar. 3, 1981 to the present inventor, discloses a method and apparatus for controlling the effect of centrifugal forces on pulp stock which is ground in a grinding space of a refiner or a defibrating apparatus between a pair of relatively rotatable grinding members. The pulp material which may consist of wood chips, bagasse, pulp fiber or similar fibrous material, is fed by a conveyor such as a screw feeder or the like, through an opening in the central portion of a stationary grinding disc into the center or "eye" of a first radially oriented inner grinding zone defined between the opposed discs. The opposed surfaces of the discs are provided with ridges and grooves which shear the fibers of the pulp or grist in grinding-like fashion. Material introduced into the "eye" of the inner radial grinding space is propelled by the centrifugal force generated by the rotational movement of the discs towards the periphery of the discs.
The apparatus disclosed in U.S. Pat. No. 4,253,613 defines a second outer grinding space which merges with the outer or peripheral end of the inner radial grinding zone. The outer grinding zone is oriented at an inclined angle relative to the inner radial grinding zone and defines a cylindrical or drum shaped grinding zone. The inner and outer grinding zones define a continuous grinding space through which pulp material introduced into the "eye" of the inner grinding space is propelled outwardly by centrifugal forces generated by the relatively rotating discs and advances through both the inner radial grinding zone and the outer inclined grinding zone. The pulp material is ejected and discharged from the open remote end of the outer inclined grinding zone into suitable discharge means. The advantages of the method and apparatus disclosed in U.S. Pat. No. 4,253,613, as more fully discussed in the patent itself, include the arrangement of the inner and outer grinding zones to efficiently control the effect of centrifugal force on the pulp stock advancing through the grinding space to increase dwell time of the pulp for enhancing the efficiency of the overall refining operation. Other advantages of the method and apparatus of U.S. Pat. No. 4,253,613 are apparent from the patent, and the disclosure of the patent is expressly incorporated by reference herein.
One disadvantage of the method and apparatus disclosed in the aforementioned patent is that adjustment of the width or gap of the inner radial grinding zone must be made separately and independently of any adjustment to the width or gap of the outer inclined grinding zone. As discussed and illustrated in the patent, the gap spacing of the inner grinding zone can be conventionally adjusted by means of an adjusting mechanism of the type more fully disclosed in U.S. Pat. No. 3,827,644. However, adjustment of the outer inclined grinding zone is made independent from the adjustment to the inner grinding zone by employing a ring member which is slideably seated in a cylindrical annular recess and actuated by a plurality of pistons connected to the ring member by means of piston rods. Simultaneous adjustment of the gap space of the inner and outer grinding zones is not possible in the prior art apparatus because adjustment of the spacing of the outer grinding zone will not result in a corresponding adjustment of the spacing of the inner grinding zone, and vice versa, as a result of the angular orientation between the inner and outer grinding zones. The need to separately and independently adjust the gap spacings of the inner and outer grinding zones is disadvantageous insofar as it requires additional control equipment and control instruments provided on the apparatus, increases the time and labor needed to adjust the grinding space, and results in greater overall costs for grinding operation.
A refiner similar to the apparatus disclosed in U.S. Pat. No. 4,253,613 is disclosed in U.S. Pat. No. 4,283,016, also issued to the present inventor. Additional background methods and apparatus for adjusting the grinding space of pulp refiners are illustrated by the following U.S. patents: U.S. Pat. Nos. 2,971,704; 3,212,721; 3,323,731; 3,295,774; 3,684,200; 3,717,308; 3,754,714; 3,790,092; 3,799,456; 3,827,644; 3,910,511; 3,974,971; 4,039,154; 4,073,442; 4,083,503; 4,269,362; 4,378,092; 4,454,991; 4,529,137; 4,614,304; and 4,627,578. None of these background references illustrated a refiner having an inner radial grinding zone and an outer inclined conical grinding zone in which both grinding zones are capable of simultaneous adjustment in a single step.
U.S. Pat. No. 4,269,362 discloses a disc refiner having only an inner radial grinding zone. The grinding elements are carried on the opposed grinding surfaces and consists of interfitting teeth defined in concentric circles. The spaces between adjacent teeth sucessively decrease toward the peripheral region of the radial grinding zone to provide a kneading or pulsating effect on the pulp propelled outwardly through the grinding zone. Means are provided to adjust the spacing between the adjacent teeth. The disclosure of this patent illustrates the use of opposed teeth only as grinding elements in a known disc refiner. This prior art patent does not recognize applicant's present invention because the teeth are not employed in any manner for simultaneously adjusting the gap spacings of two different grinding zones in a single step, the primary object of the present invention as is discussed herein.